英语语法分析

Cepheids are reliable cosmic distance mileposts. The interval it takes for the Cepheid to complete one pulsation is a direct indication of the stars'; s intrinsic brightness.

造父变星是可靠的宇宙距离(测量)里程碑，其完整的一个光变周期直接反映了星体的本质光亮度。